Methods and systems of vibrating a screen

ABSTRACT

Screen vibration systems are provided that can vibrate theater screens using acoustical, electromagnetic, or another type of energy while reducing the presence of image artifacts that may otherwise be visible as result of vibrating the screen. In one example of a screen vibration system, the system includes a screen, a permanent magnet mounted to the screen, and a magnetic source positioned with respect to the permanent magnet and uncoupled from the screen. The screen is moveable in response to a changing magnetic field from the magnetic source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 14/786,353,titled “METHODS AND SYSTEMS OF VIBRATING A SCREEN, and filed Oct. 22,2015, which is a U.S. national phase under 35 U.S.C. 371 ofInternational Patent Application No. PCT/IB2014/061331, titled “METHODSAND SYSTEMS OF VIBRATING A SCREEN” and filed May 9, 2014, which claimsthe benefit of U.S. Provisional Application No. 61/821,311, titled“METHODS AND SYSTEMS OF VIBRATING A SCREEN” and filed May 9, 2013, eachof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to the field of displayingimages and, particularly but non-exclusively, to enhancing displayedlaser images.

BACKGROUND

Shaking display screens can enhance displayed images on the screen.Projecting an image on a stationary screen using a coherent light sourcesuch as a laser light source can result in visual artifacts (known asspeckle) in the image area. By shaking the screen surface on which animage is projected, speckle artifacts can be reduced or eliminated. Toensure speckle is reduced over all of the image area on the screen, allof the screen area is shaken. It can be desirable to have more than onepoint or source of screen vibration to achieve vibrating all of theimage area of the screen. Screens can have a large surface area composedof a material, such as vinyl, that absorbs sufficient vibration energyimparted to the screen that the screen requires multiple vibrationlocations.

Using multiple sources to vibrate the screen, however, can introduceproblems.

SUMMARY

In one example, a screen vibration system is provided. The screenvibration system includes a screen, a permanent magnet mounted to thescreen, and a magnetic source positioned with respect to the permanentmagnet and uncoupled from the screen. The screen is moveable in responseto a changing magnetic field from the magnetic source.

In another example, a method to vibrate a screen is provided. Apermanent magnet is mounted onto the screen. An electromagnet ispositioned across from the permanent magnet. An electric current to theelectromagnet is controlled to successively repel and attract thepermanent magnet to cause the screen to vibrate.

In another example, a system to vibrate a screen is provided. The systemincludes a first actuator and a second actuator. The first actuator ispositioned behind the screen at a first location for moving the screenat the first location based on a first electric signal. The secondactuator is positioned behind the screen at a second location for movingthe screen at the second location based on a second electric signal thatis uncorrelated with respect to the first electric signal.

In another example, a method for vibrating a screen is provided. A firstelectromechanical acoustic actuator and a second electromechanicalacoustic actuator are positioned behind the screen. The firstelectromechanical acoustic actuator is driven using a first electricsignal. The second electromechanical acoustic actuator is driven using asecond electric signal that is de-correlated with respect to the firstelectric signal. The screen is caused to vibrate by the firstelectromechanical acoustic actuator and the second electromechanicalacoustic actuator.

In another example, a method for reducing speckle artifacts is provided.A screen is vibrated by a screen vibrator. Information about a projectedimage on the screen is captured using a sensor. An amount of speckleartifacts present in the projected image on the screen is determinedfrom the captured information. A signal to a controller that drives thescreen vibrator is controlled in response to comparing the amount ofspeckle artifacts to a predetermined threshold.

In another example, a system to vibrate a screen is provided. The systemincludes an electromechanical acoustical actuator with an open baffle.The electromechanical acoustical actuator is uncoupled from the screenin an operational setup. The system also includes a controller toprovide an electrical signal to the electromechanical acousticalactuator for causing the electromechanical acoustical actuator to outputenergy to displace air that is (i) in front of the electromechanicalacoustical actuator and (ii) between the electromechanical acousticalactuator and the screen. The open baffle is configured for preventingdisplaced air behind the electromechanical acoustical actuator fromaffecting the screen.

In another example, a system is provided. The system includes a screenfor displaying an image, a laser projector to project the image towardthe screen, at least two vibrator assemblies positioned to vibrate thescreen, and a controller to control the at least two vibrator assembliesusing uncorrelated control signals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a system for vibrating a screen according toone example.

FIG. 2A is a cross-sectional side view of a first example of a bafflewith respect to a screen and an actuator for vibrating the screen.

FIG. 2B is a perspective view of the baffle and the actuator of FIG. 2A.

FIG. 3A is a cross-sectional side view of a second example of a bafflewith respect to a screen and an actuator for vibrating the screen.

FIG. 3B is a perspective view of the baffle and the actuator of FIG. 3A.

FIG. 4A is a cross-sectional side view of a third example of a bafflewith respect to a screen and an actuator for vibrating the screen.

FIG. 4B is a perspective view of the baffle and the actuator of FIG. 4A.

FIG. 5 is a schematic of a screen vibration system that includes arotatable permanent magnet according to one example.

FIG. 6 is a schematic of the screen vibration system of FIG. 5 with therotatable permanent magnet in a non-vibrating position according to oneexample.

FIG. 7 is a schematic of a screen vibration system using a stationaryelectromagnet according to one example.

FIG. 8 is a schematic of a screen vibration system that includes acontroller and a stationary electromagnet according to one example.

FIG. 9 is a back view of a screen with battens mounted on the screenaccording to one example.

FIG. 10 is a schematic a coil driver configuration according to oneexample.

FIG. 11 is a block diagram of a system for outputting a signal on anoutput channel that is uncorrelated with other channels according to oneexample.

FIG. 12 is a schematic of a system for reducing speckle in a theatreaccording to one example.

FIG. 13 is a flow chart of a process for reducing speckle according toone example.

FIG. 14 is a schematic of an automatically adjustable screen vibrationsystem according to one example.

DETAILED DESCRIPTION

Certain aspects, features, and examples of the present disclosure relateto a screen vibration system that can vibrate a theatre screen usingacoustical, electromagnetic, or another type of energy while reducingthe presence of image artifacts that may otherwise be visible as resultof vibrating the screen.

Screens supported by a screen support structure can have a mass in theorder of a couple hundred or more kilograms. One approach to shaking thescreen is to distribute vibrating sources that can shake the screen overthe area of the screen. Applying a small amount of energy to each of thevibrating sources can collectively shake the whole screen.

One challenge can include moving the screen in a way that does notcreate screen distortion artifact visible by someone in the audience. Ascreen distortion artifact can be a local physical distortion that isvisible on the screen surface and that is inconsistent with other areasof the screen surface. A screen with a high-gain coating on its surfacecan be susceptible to slight local distortions where a discontinuity inthe screen's perceived gain can be recognized when the screen is pokedor pulled by devices intended to vibrate the screen. Creating a localphysical distortion in the screen position can cause the lightreflection of the distorted portion of the screen surface to appear tobe inconsistent with light reflected from areas of the screen withoutthe local distortion. Deformations in the screen surface can appear asluminance distribution distortions.

A screen without a vibration system can have a surface profile that isthe screen's natural resting state surface profile. A screen can beequipped with a vibration system that does not distort the screensurface profile from its natural resting surface profile. The screenvibration system can avoid exerting a biased force on the screen whenthe screen vibration system is inactive or not powered on. When thescreen vibration system is actively vibrating the screen, the averagedisplacement position of the screen can be the same position of thescreen in its natural resting state.

To reduce speckle artifacts, the screen vibrations can avoid creatinglarge screen displacements that can otherwise be visible to a viewer.Displacements can be limited to small amounts in such a way that thescreen displacement variation can be unnoticed to the viewer, but thedisplacement can be sufficient to cause speckle artifacts to be reducedor eliminated. The displacement amplitude of the screen to reducespeckle can vary. For example, the amplitude of the screen displacementcan be greater at the location of the screen vibrator, but at a distancefurther away from the screen vibrator the screen displacement can beless and still reduce speckle artifacts. The frequency of the screendisplacement can be above a certain level to avoid the displacementbecoming easily perceptible. But the higher the frequency of the screendisplacement, the more audible the vibration system may become. Therecan be a limited range of frequencies and amplitudes of screendisplacement that can provide an optimum tradeoff of speckle artifactreduction with minimizing audience perceptibility of the screen beingdisplaced and possible audible noise from vibrating the screen. Therange of screen displacement frequencies can be within a range of 10 Hzto 35 Hz, although speckle reduction can still occur using displacementfrequencies outside of the range.

The screen surface can be designed to vibrate by making physicalcontact, for example from behind the screen, with a mechanicallyvibrating surface. In other examples, the screen is shaken using anon-contact approach. An example of the non-contact approach can be byan acoustical component with an electromechanical acoustical transduceror actuator, such as a loudspeaker, being placed behind the screen andin close proximity to the screen. When the acoustical transducer isactivated with a low frequency signal, the transducer can displace theair directly behind the screen to induce screen movement with the samefrequency by which a transducer is moving. The acoustical transducer canhave a moving cone or diaphragm to displace the air. The frequency ofthe signal to the acoustical transducer can be above or below themaximum hearing range of a human to avoid audible detection by theaudience. The acoustical transducer vibration system can allow thescreen surface to rest in a natural state profile when the transducer isnot active and can allow the screen to be displaced equally in the twodirections when the transducer is active.

FIG. 1 shows one example of a system for screen vibration. The systemincludes an actuator 104 that can receive a signal from a power supply106. The actuator 104 is positioned behind a screen 102. The actuator104 can displace the air directly behind the screen 102 to displace thescreen 102 with a frequency of the signal from the power supply 106. Insome examples, the actuator 104 is an acoustical actuator.

In another example, an electromechanical acoustical actuator is fit witha baffle to vibrate a screen. FIGS. 2A to 4B are examples of differentbaffles fitted to the actuator 104 that is positioned to face the screen102. The actuator 104 can be placed a distance from the screen 102 thatis in the range of a one-quarter inch to twenty-four inches. Adding abaffle can cause the air between the screen 102 and the actuator 104 tobe influenced by a surface of the actuator 104 that is facing the screen102 to maximize screen displacement. When the actuator 104 moves air,the air on one side of the actuator 104 experiences a positivecompression and the air on the other side of the actuator 104experiences a negative compression. The displaced air on the two sidesof the actuator 104 can be of opposite polarity or 180 degrees out ofphase. Displacements of air with opposite polarity that interact canhave a net effect of reducing or canceling the net displacement of air.Having a baffle restrict the opposite polarity of displaced air at thesurface of the actuator 104 not facing the screen 102 from influencingthe air at the screen 102 can prevent an undesirable reduction in airdisplacement at the screen 102. Beyond the baffle, the displaced airfrom the front and the back of the actuator 104 can interact and cancause partial or full cancellation at locations further away from theactuator 104 and baffle, such as locations at which an audience viewingthe screen can be located.

FIG. 2A depicts a cross-sectional side view of a baffle 250. The baffle250 can be a plate that separates any displacement of air towards thescreen 102 caused by the front of the actuator 104 from interacting withthe displacement of air that occurs at the back of the actuator 104. Thesurface of the baffle can be positioned parallel to the screen 102 andnormal to an acoustical axis of the actuator 104. The acoustical axiscan be a centerline along the direction that air is being displaced bythe actuator 104. The actuator 104 can be an acoustical transducer of aconfiguration used in an acoustical loudspeaker such as anelectromechanical transducer with a cone or other diaphragm movedelectromechanically. FIG. 2B depicts a perspective view of the actuator104 and the baffle 250. The face 252 (i.e., the side facing the screen102) of the baffle 250 and the actuator 104 is shown in FIG. 2B. Thebaffle 250 can be a stiff material or a dense material to prevent airdisplacements from flexing the baffle, further reducing any interactionbetween displaced air in the front and in the back of the actuator 104.The baffle 250 can be rectangular, circular or another shape suitablefor a specific implementation.

FIG. 3A depicts another example of a baffle 360 by cross-sectional sideview. The baffle 360 is tubular, the face 362 is shown by perspectiveview in FIG. 3B, to separate the displacement of air that occurs betweenfront of the actuator 104 and the back of the actuator 104. Theacoustical axis of the actuator 104 can be parallel to an axis of thetubular baffle 360 and at a right angle to the screen 102. The openingof the baffle 360 can be positioned to face the screen 102. The actuator104 can be an electromechanical transducer with a cone. The baffle 360can be a stiff material or a dense material. The cross-sectional shapeof an opening of the baffle 360 can be rectangular, circular, or anothershape suitable for a specific implementation. The baffle 360 can extendbehind the actuator 104. In other examples, the baffle 360 can extend infront of the actuator 104 or the baffle 360 can extend behind and infront of the actuator 104.

FIG. 4A depicts by cross-sectional side view another example of a baffle470 that includes a plate 474 and a tubular (or other shaped) structure476 extending from the plate 474. FIG. 4B depicts a perspective view ofbaffle 470 and actuator assembly 104 that can be in a face direction 472toward the screen.

The open baffles described above can allow for vibrating an area of thescreen 102 that is in close proximity to the actuator 104 with littlecancellation effects yet allowing cancellation effects of thepropagating low frequency air disturbances to occur at distances beyondthe baffle mounted to the actuator 104.

Another approach to vibrate a screen can include positioning a magneticsource in close proximity to the screen in which a magnetic force can beused to repel and attract an element attached to a back surface of thescreen.

FIGS. 5 and 6 depict an example of screen vibration using permanentmagnets. Mounted onto the screen 102 is a batten 504 with an element 506that can interact with a permanent magnet 512 a. The permanent magnet512 a is mounted to a motor shaft 510 and the permanent magnet 512 a canbe rotated by the motor 508 with power from a power supply 106. If theelement 506 is a permanent magnet with a North/South orientation, asshown, the rotating permanent magnet 512 a can push the element 506outwards when the North pole of the permanent magnet 512 a is orientedtowards the element 506. When the permanent magnet 512 a rotated to beoriented with the South pole positioned next to the element 506, theelement 506 can be attracted towards the permanent magnet 512 a. If theelement 506 is metal that can be influenced by a magnetic field such asiron instead of a permanent magnet, the element 506 may only movetowards the permanent magnet 512 a regardless of the North or Southorientation of the magnetic field facing the element 506. The screendisplacement may be only in one direction, e.g., towards the permanentmagnet 512 a. Having the element 506 as a permanent magnet, however, maybe useful if the average screen displacement over time is desired to beclose to the natural rest position of the screen. The frequency withwhich the element 506 moves in and out can be directly proportional tothe speed at which the permanent magnet 512 a rotates. The rotationalrate can be adjusted using the power supply 106 to the desired frequencyof vibration. The screen 102, when displaced outwards from the permanentmagnet 512 a, may have less displacement from the rest position of thescreen 102 when the screen 102 is displaced towards the permanent magnet512 a. The system can compensate for the difference by reducing thelength of the permanent magnet 512 a for the portion that attracts theelement 506 such that the outward and inward displacements are equal toachieve equal inwards and outwards screen displacement. When the screenvibration system is not active, the permanent magnet 512 a can bepositioned as shown in FIG. 6 such that its influence on the element 506is minimized and the screen 102 remains in a natural rest position.

FIG. 7 depicts an example of a screen vibration system that uses astationary electromagnet system. A coil 720 of wire is positioned on acore 722 and is oriented such that the end of the core 722 is directedtowards the element 506. If the core 722 is of a material, such as iron,that is influenced by a magnetic field, a small amount of electricalcurrent can be made to pass through the coil 720 by power supply 106 tocreate a magnetic field that can repel or attract the element 506. Whenthe current through the coil 720 traveling in the reverse direction, themagnetic field can become opposite than before and can attract theelement 506 instead of repelling (or repel instead of attracting,depending on setup). The screen displacement that results from forcingthe element 506 to move by the magnetic field can displace the screen102 in either direction.

The screen 102, when displaced outwards from the electromagnet formed bythe coil 720 and core 722, may have less displacement from a restposition than when the screen 102 is displaced towards theelectromagnet. This difference can be compensated for by increasing theelectric current to the coil 720 such that there is more current goingthrough the coil 720 when the coil 720 repels the element 506 than whenthe coil 720 is attracting the element 506. The current can be shapedinto an asymmetrical waveform to provide a screen displacement that isequal in both directions from the rest position of the screen 102. Oneapproach is to measure the screen displacement profile for a givensignal waveform to the electromagnet and determine how the input signalis to be modified to provide the desired screen displacement. Themodified waveform is then applied to the electromagnet to confirm thedesired displacement profile has been achieved. A range finder sensorcan be used to measure the screen displacement. Another approach tocreating an asymmetrical waveform is to add a direct current bias in theamount that achieves an average screen displacement that is the same asthe natural rest position of the screen.

Changing the magnetic field in the system in FIG. 7 can influence theelement 506 associated with the screen 102. If the frequency of thechanging magnetic field increases, the force exerted by the changingmagnetic field may not be able to overcome the combined inertia of thescreen 102, the batten 504, and the element 506 to make the screen 102follow the changing magnetic field. If the maximum frequency that thevibration system (e.g., the magnetic system) is able to influence thescreen 102 is too low, the inertia of the screen 102, the batten 504,and the element 506 can be reduced to raise the upper limit at which thescreen 102 can be vibrated. Using more powerful electromagnets andelectromagnetic drivers can also increase the upper limit at which thesystem is able to vibrate the screen 102. Screen tension may also be afactor in that the more tension there is on the screen 102, the amountof force needed to displace the screen 102 is greater. Reducing screentension can help increase screen vibration displacement and increasingthe screen vibration frequency. But too much reduction in screen tensioncan lead to other screen surface artifact problems such as screen sag.

When no current is passing through the coil 720 in FIG. 7, only theattractive magnetic force present can be from the element 506 to thecore 722. This may create a slight residual force on the element thatcan pull the screen 102 slightly towards the core 722. One approach toreducing the residual force is to move the core 722 and coil 720 furtheraway from the element 506 and use a higher electric current in the coil720 to increase the magnetic field to compensate for the increaseddistance. Another approach can include changing the material from whichthe core 722 is made to a material that is not influenced by a magneticfield. Examples of these types of materials include plastic, aluminumand air. When a material that is not influenced by a magnetic field isused for the core 722, more current may be needed to achieve the samemagnetic field strength compared to a core that is made from iron. Thenumber of turns of wire used in the coil 720 can be increased to achievea higher magnetic field. The coil 720 can be placed closer to theelement 506 when a core that is not influenced by a magnetic field isused.

FIG. 8 shows an example of a screen vibration system with a controller806 to control electrical current through an electromagnetic device thatincludes a coil 820 and a core 822. The magnetic flux path through airgaps can be significantly reduced to allow more efficient energytransfer from the actuating device (i.e., the coil 820 and the core 822)to a permanent magnet 806 and a batten 804 on the screen 802. Wherethere is more efficient magnetic coupling, the magnetic field can bemore contained to provide better energy transfer to the screen 102 andcan be performed by configuring the permanent magnet 806 on a screenbatten 804 and the electromagnetic core 822 to form a more complete loopor closed loop with reduced air gap for the magnetic fields to passthrough. The electromagnetic core 822 can be made from a metallicmaterial that is influenced by a magnetic field. The metallic materialmay have a high relative permeability characteristic. Examples ofmetallic materials that have a high relative permeability can beferromagnetic metals such as iron or Mu-metal. The air gaps in themagnetic flux path may be limited to the shorter paths between the endsof the core 822 and the permanent magnet 806. Energy efficiency of thevibration system can be improved by configuring the electromagnetic coreand the permanent magnet on the screen batten so that there are no largeair gaps at the open ends.

The elements 506, 806 described above can each be mounted in a batten504, 804 to distribute the repelling and attractive forces exerted onthe element 506, 806 over a larger area of the screen 102. For example,the length of the batten 504, 804 can be one foot to two feet long andone inch or more wide. For a screen with only a horizontal curvature andno vertical curvature, one or more battens can be mounted vertically onthe back of the screen. The battens can be made of a light yet stiffmaterial, such as balsa wood, carbon fiber, or a composite material. Theelement 506, 806 can be mounted on the surface of the batten 504, 804 orrecessed in the batten 504, 804. The batten 504, 804 can be fastened tothe screen 102 by adhesive that does not cause a deformity or a stain onthe screen 102 to occur. The side of the batten 504, 804 towards thescreen 102 can be black in color such that it is not visible if thescreen 102 is perforated. Perforated screens may be used, for example,where audio loudspeakers are positioned behind the screens and thepresentation sound can pass through the openings in the screen material.

FIG. 9 shows the locations of a possible batten distribution of battens932 mounted onto a screen 930. The larger the screen the more battenscan be used or needed.

A suitable power source can be used to power each coil for the locationswhere battens are located over the screen. One approach is to use onepower source that powers all of the coils so that all of the coilsvibrate at the same frequency and in phase. The screen vibrations,however, may have the same frequency and phase relationship, which canresult in localized standing vibration wave patterns distributed overthe screen. Standing wave vibrations may not be effective at reducingspeckle because a component of the displaced screen is not moving andtherefore may be unable to reduce speckle artifacts.

One approach that may be used to reduce or eliminate standing vibrationwaves is to power or drive each of the coils with a separate source suchthat each source generates random signals that are uncorrelated (alsoreferred to as “de-correlated”). The random signals can be random inamplitude and in frequency, similar to pink or white noise. If thesignal is random in amplitude and not in frequency, or random infrequency but not in amplitude, there may still be a standing componentin the interactions of the waveforms from different sources. The signalsfrom each of the vibration sources can be de-correlated in amplitude andin frequency. For example, each of the coils can be driven with a signalthat has a different amplitude, frequency, and phase relationship thansignals used to drive the other coils to reduce or eliminate theconditions that lead to standing waves or having a component of astanding wave.

FIG. 10 schematically depicts an example of a coil driver configurationfor a screen vibrations system. Each of the coils 1-n 1050, 1052, 1054,1056 can be electrically connected to an actuator driver power supply1040. The actuator driver power supply is configured (such as by beingdesigned) to have channel outputs 1042, 1044, 1046, 1048 to provide asignal for each coil. Each channel can be configured with its ownfrequency source in which the frequency source is a random frequencysource, such as a pink or a white noise source. The bandwidth of thefrequency source can be such that there are frequency components in the20 Hz to 30 Hz range so that when the frequency source is filtered witha 20 Hz to 30 Hz bandpass filter there is signal content.

FIG. 11 shows a block diagram of system 1100 for outputting a signal onan output channel that is uncorrelated with other channels. Each of thechannel outputs 1042, 1044, 1046, 1048 in FIG. 10 from the actuatordriver power supply 1040 can be fed by separate systems within theactuator driver power supply 1040, an example of one of which is shownin FIG. 11. The frequency source 1160 can be a DSP or other type ofsignal processor in which a range of random frequencies can be produced,such frequencies corresponding to pink noise or white noise. A bandpassfilter 1162 can filter the signal from the frequency source 1160 toremove unuseful portions of the signal for the screen vibration coil isused. A screen vibration range can be 20 Hz to 30 Hz, but it is notlimited to this range. The filtered source signal is amplified with anamplification circuit 1164 so that the signal level is appropriate forthe screen vibration coil. Each channel can have its own frequencysource so that the signal from each channel can be uncorrelated. Thesame driver configuration can be used to drive other actuators in placeof the coil 720 and the coil 820, in FIGS. 7 and 8 respectively, such asthe actuator 104 or motor 508.

Certain examples of screen vibration systems disclosed here can beretrofitted onto existing theatre screens, including screens in theatresin which the projection system image light source has been changed froma non-coherent light source to a coherent light source, such as a laserlight source.

To optimize speckle artifact reduction, a screen image monitoring systemand feedback loop can be set up to adjust the amount of vibration oralter a vibration parameter applied to the screen vibrator. FIG. 12shows a system that can be used to optimize speckle reduction in atheatre. A theatre screen 1202 may have a number of screen vibrators1212 a-c positioned behind the screen and that are controlled by acontrol unit 1214. The control unit 1214 can provide de-correlated drivesignals to each of the vibrators 1212 a-c such that the screen 1202 isvibrated by each vibrator and the screen vibrations can be de-correlatedwith respect to each other. When a projector 1204 is projecting lightthrough the projection lens 1206 onto the screen 1202, a sensor 1208,such as a camera, can capture the projected light on the screen 1202.The captured image can be stored within the sensor 1208 or in a separateunit 1210. The separate unit 1210 can also process the camera image toanalyze and determine or quantify the amount of speckle in the light onthe screen 1202. The information from the separate unit 1210 can becommunicated to the control unit 1214, which can provide the drivesignal to each of the screen vibrators 1212 a-c. The sensor 1208 can belocated in the projection booth with the projector 1204 or the sensor1208 can be positioned outside the projection booth such that the sensor1208 is not required to view the screen 1202 through the booth window1216. The separate unit 1210 can be on its own or part of the sensor1208, part of the projector 1204, or part of the control unit 1214.

The process to optimize reducing speckle can be performed by projectinglight onto the screen 1202 from the projector 1204. Projected light canbe a projected pattern or it can be just one color projected over thewhole screen area. For example, the light projected onto the screen 1202can be blue, red, or green. The optimization can be performed for onecolor, such as green light, in which speckle artifacts are known to bemore apparent or the optimization can be performed to ensure speckleartifacts reduction is optimized in consideration of all light colors.The optimization to reduce speckle can be performed before a day ofshows or scheduled to reoccur over a longer period of time. The sensor1208 can be a camera that captures the projected light pattern intendedfor speckle reduction. The captured image could be processed andanalyzed for the amount of speckle present by the separate unit 1210.The amount of speckle can be determined globally for the screen 1202 orthe speckle can be determined for more localized areas of the screen1202, such as the screen areas influenced by the vibrators 1212 a-c.Based on predetermined criteria as to the amount of speckle that isacceptable compared to the amount of speckle present, the control unit1214 can be influenced by the information from the separate unit 1210 tochange the signal to the vibrators 1212 a-c to achieve the specklereduction required.

An example of a process 1300 to reduce speckle artifacts is shown as aflow chart in FIG. 13. The process 1300 is described with reference tothe system diagram shown in FIG. 12, but other implementations arepossible. In block 1302, the image light on the screen 1202 is capturedwith the sensor 1208. In block 1304, the separate unit 1210 processesthe captured image for speckle artifact analysis. Processing thecaptured image for speckle artifact analysis may include low-frequencyfiltering of the image to further isolate speckle artifacts. In block1306, the separate unit 1210 determines the amount of speckle artifactspresent on the screen 1202 from the processed information. In block1308, a comparison of the present amount of speckle artifact is madewith a threshold level. In decision block 1310, further action isdetermined based on this comparison. If the present amount of speckledoes not exceed a threshold, no further adjustment is required as inblock 1312. If the present amount of speckle exceeds acceptable limits,then a corrective adjustment to be applied to one or more of the screenvibrators 1212 a-c is determined in block 1314. One or more of thescreen vibrators 1212 a-c receives the corrected vibration signal andthe screen 1202 is vibrated with a corrective adjustment to the screenvibrator(s) in block 1316. The process 1300 of FIG. 13 can be repeatedto determine if the corrective adjustment has reduced the amount ofspeckle to within the predetermined threshold limit. If, after apredefined number of iterations of the process 1300, the amount ofspeckle is not reduced to within the predetermined threshold limits, thecondition can be flagged. When flagged, other factors such asrepositioning of a screen vibrator can be considered. Re-positioning canbe performed manually or with a vibrator system as described in FIG. 14that is automated.

Screen vibrators may need to be repositioned over time to maintain anoptimum distance between the vibrator and the screen. A vibrator orvibrator assembly that is hard mounted to the screen frame or otherconnection point may not be adjustable to accommodate changes indistance between the vibrator and the screen that may occur over time orwith a change in temperature and humidity.

An adjustable configuration 1400 shown in FIG. 14 has a vibratorassembly 1414 with a baffle 1450 and can be mounted onto a movableportion 1402 of a platform assembly where the stationary portion 1404 ofthe platform assembly is mounted to the screen structure (not shown).The platform assembly can have a motor or actuator 1406 that can becommanded to move the movable portion 1402 of the platform to move thevibrator assembly 1414 closer or further away from the screen 102. Thevibrator assembly 1414 and baffle 1450 may be replaced with anon-acoustical electromagnetic actuator assembly, examples of which aredescribed in FIGS. 5, 7 and 8.

In another configuration, the distance between the vibrator and thescreen can be adjusted by mounting the vibrator assembly so that it canmove, slide or pivot small distances closer or further away from thescreen. By controlling with a motor or actuator the amount of move,slide, or pivot of the vibrator assembly with respect to the screen, thedistance between the vibrator and the screen can be adjusted. Apantograph mechanism may also be employed to allow the vibrator assemblyto be repositioned with respect to the screen while maintaining aconstant angular relationship with the screen.

In the automated adjustment system shown in FIG. 14, a distance sensingdevice 1408 can be mounted on the vibrator assembly 1414 to determinethe distance 1410 that the vibrator assembly 1414 is from the screen102. The distance sensing device 1408 can be an ultrasonic distancesensor or a distance sensor that utilizes alternate distance sensingtechnology. A processor within the controller assembly 1412 can be usedto receive distance information from the distance sensing device 1408and determine whether or not the vibrator assembly 1414 is within theacceptable distance range from the screen 102. If the distance 1410 isnot acceptable, the processor commands the motor driver in thecontroller assembly 1412 to make the actuator 1406 move the movableportion of the platform with the vibrator assembly 1414 attached untilit is within an acceptable distance range between the vibrator assembly1414 and the screen 102. If the vibrator assembly 1414 remains in theacceptable distance range from the screen 102, the processor may commandthe controller assembly 1412 to hold the current motor position.

Each screen vibrator can be configured to be automatically adjustedbetween the screen and the vibrator. In another example, only the screenvibrators in screen locations where there is a greater tendency for thedistance between the screen and the vibrator to change over time. Forexample some portions of the screen can experience more sag with timethan other portions of the screen and therefore the vibrators positionedwith portions of the screen experiencing more sag can be configured sothe distance between the vibrator assemblies and the screen can beadjusted. In one configuration, vibrators positioned at the lowerportion of the screen can be vibrators in which their distance to thescreen can be adjusted.

In another example, the position between the vibrator and the screen canbe optimized in a screen tuning process. For example, the system in FIG.12 can be designed by configuring screen vibrators 1212 a-c to beadjustable vibrators of a configuration described in FIG. 14. Thecontroller assembly 1412 can be configured to receive information basedon the amount of speckle from the separate unit 1210 or the control unit1214 in FIG. 12. In a screen tuning process, the information receivedfrom the separate unit 1210 or the control unit 1214 can be commands tochange the distance between the vibrator and the screen to optimizereducing speckle and minimize the amount displacement in the screenvibration. The speckle reducing optimization and screen tuning processcan occur as part of a daily system calibration, or before eachpresentation or during a presentation or as required.

In another example, the signal from the distance sensing device 1408, onthe vibrator assembly 1414 in FIG. 14 can be provided to the controlunit 1214 of FIG. 12 to control the amplitude of the signal to thecorresponding vibrator by the control unit 1214 to maintain a screenvibration that compensates for changes in distance between the vibratorand the screen.

In an alternate configuration where multiple screen vibrators are usedand are all driven by substantially the same non-decorrelated signal,standing wave artifacts can be minimized by keeping each screen vibratora certain distance away from adjacent screen vibrators, such that therespective vibration displacement waves have minimal interference withone another. The distance between each screen vibrator can also be asclose as needed to ensure there are no areas on the screen that do notreceive the adequate amount of vibration but not too close of a distanceto create visible standing waves that form as a result of theinterference of the two waves from the two adjacent screen vibrators.Where a screen vibration speckle reduction feedback loop is being used,the global speckle artifact reduction can be optimized for a commonvibrator drive signal. Optimization can also include adjusting theamplitude of the drive signal to a different level for each screenvibrator even though all the vibrators are driven at the same frequency.

The foregoing description of the aspects, including illustrated aspects,of the invention has been presented only for the purpose of illustrationand description and is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Numerous modifications,adaptations, and uses thereof will be apparent to those skilled in theart without departing from the scope of this invention.

What is claimed is:
 1. A screen vibration system, comprising: aplurality of vibrator assemblies positionable proximate to a surfacearea of a screen on which images are displayed, the plurality ofvibrator assemblies being configured to displace the screen, wherein aposition of at least one vibrator assembly of the plurality of vibratorassemblies is adjustable based on a change in screen location fromscreen sag.
 2. The screen vibration system of claim 1, wherein the atleast one vibrator assembly is moveable by a pantograph mechanism tochange the position of the at least one vibrator assembly.
 3. The screenvibration system of claim 1, wherein the position of each vibratorassembly of the plurality of vibrator assemblies with respect to thescreen is adjustable independent of other vibrator assemblies of theplurality of vibrator assemblies.
 4. The screen vibration system ofclaim 1, wherein the plurality of vibrator assemblies is configured tovibrate the screen such that an average displacement of the screenduring vibration is the same location of the screen in a natural reststate.
 5. The screen vibration system of claim 1, wherein the pluralityof vibrator assemblies comprise a plurality of electromagnetic actuatorassemblies configured for displacing at least some portions of thescreen by vibrating and causing the portions of the screen to move. 6.The screen vibration system of claim 5, wherein the plurality ofvibrator assemblies is configured to cause a direction of displacementto the screen such that at least some portions of the screen arerepelled from the plurality of vibrator assemblies or attracted to theplurality of vibrator assemblies.
 7. The screen vibration system ofclaim 5, wherein each electromagnetic actuator assembly of the pluralityof electromagnetic actuator assemblies includes a coil through which anelectrical current is transmittable for creating a magnetic field torepel or attract an element that is influenced by the magnetic field tocause the screen to be displaced.
 8. The screen vibration system ofclaim 5, wherein each electromagnetic actuator assembly of the pluralityof electromagnetic actuator assemblies includes an electromechanicaltransducer with a diaphragm that is movable electromechanically to causethe screen to be displaced.
 9. The screen vibration system of claim 5,wherein each electromagnetic actuator assembly includes a magneticsource positionable with respect to the screen for providing a magneticforce to which an element is responsive by being repelled or attractedto cause the screen to be displaced.
 10. The screen vibration system ofclaim 1, further comprising: a platform with a moveable portion on whichthe at least one vibrator assembly of the plurality of vibratorassemblies is coupled; and a controller assembly configured for causingthe movable portion of the platform to move and change the position ofthe at least one vibrator assembly of the plurality of vibratorassemblies.
 11. The screen vibration system of claim 10, wherein theplatform includes a stationary portion that is mountable to a screensupport structure.
 12. The screen vibration system of claim 11, whereinthe position of the at least one vibrator assembly of the plurality ofvibrator assemblies is automatically adjustable based on a change overtime in screen location from screen sag.
 13. The screen vibration systemof claim 12, further comprising: a distance sensor coupled on the atleast one vibrator assembly and configured for providing distanceinformation that comprises a distance between the at least one vibratorassembly and the screen, wherein the controller assembly is configuredto receive the distance information and cause the position of the atleast one vibrator assembly of the plurality of vibrator assemblies tochange to maintain the distance within a distance range automatically.14. The screen vibration system of claim 13, wherein the controllerassembly includes a motor driver that is configured to control aplatform actuator for causing the movable portion of the platform tomove.
 15. A method for vibrating a screen, the method comprising:driving a vibrator assembly, located behind the screen, using anelectric signal to vibrate the screen; automatically changing a positionof the vibrator assembly behind the screen to a new position, based on achange in a screen location of at least a portion of the screen fromscreen sag; and driving the vibrator assembly located at the newposition to vibrate the screen.
 16. The method of claim 15, furthercomprising: automatically changing positions with respect to the screenof each vibrator assembly of a plurality of vibrator assembliesindependent of other vibrator assemblies of the plurality of vibratorassemblies.
 17. The method of claim 16, further comprising: vibratingthe screen by the plurality of vibrator assemblies such that an averagedisplacement of the screen during vibration is the same location of thescreen in a natural rest state.
 18. The method of claim 17, whereinvibrating the screen by the plurality of vibrator assemblies includescausing a direction of displacement to the screen such that at leastsome portions of the screen are repelled from the plurality of vibratorassemblies or attracted to the plurality of vibrator assemblies.
 19. Themethod of claim 15, further comprising: providing, by a distance sensorcoupled to the vibrator assembly, distance information that comprises adistance between the vibrator assembly and the screen; and causing theposition of the vibrator assembly to change to maintain the distancewithin a distance range automatically.
 20. The method of claim 19,further comprising: controlling a platform actuator for causing amovable portion of a platform coupled to the vibrator assembly to moveto change the position of the vibrator assembly.
 21. A system,comprising: a screen having a surface on which images are displayable,the screen being susceptible to screen sag that changes a location of aleast part of the screen; and a vibrator assembly positioned withrespect to a side of the screen that is opposite to the surface on whichimages are displayable, the vibrator assembly comprising an actuator forvibrating at least a portion of the screen, the vibrator assembly beingmoveable to change a position of the vibrator assembly with respect tothe screen in response to the portion of the screen changing location asa result of screen sag.
 22. The system of claim 21, wherein the vibratorassembly is a plurality of vibrator assemblies, wherein the position ofeach vibrator assembly of the plurality of vibrator assemblies withrespect to the screen is adjustable independent of other vibratorassemblies of the plurality of vibrator assemblies.
 23. The system ofclaim 22, wherein the plurality of vibrator assemblies is configured tovibrate the screen such that an average displacement of the screenduring vibration is the same location of the screen in a natural reststate.
 24. The system of claim 22, wherein the plurality of vibratorassemblies comprise a plurality of electromagnetic actuator assembliesconfigured for displacing at least some portions of the screen byvibrating and causing the portions of the screen to move.
 25. The systemof claim 24, wherein each electromagnetic actuator assembly of theplurality of electromagnetic actuator assemblies includes a coil throughwhich an electrical current is transmittable for creating a magneticfield to repel or attract an element that is influenced by the magneticfield to cause the screen to be displaced.
 26. The system of claim 24,wherein each electromagnetic actuator assembly of the plurality ofelectromagnetic actuator assemblies includes an electromechanicaltransducer with a diaphragm that is movable electromechanically to causethe screen to be displaced.
 27. The system of claim 24, wherein eachelectromagnetic actuator assembly includes a magnetic sourcepositionable with respect to the screen for providing a magnetic forceto which an element is responsive by being repelled and attracted tocause the screen to be displaced.
 28. The system of claim 21, furthercomprising: a platform with a moveable portion on the vibrator assemblyis coupled; and a controller assembly configured for causing the movableportion of the platform to move and change the position of the vibratorassembly.
 29. The system of claim 28, further comprising: a distancesensor coupled on the vibrator assembly that includes the actuator, thedistance sensor being configured for providing distance information thatcomprises a distance between the vibrator assembly and the screen,wherein the controller assembly is configured to receive the distanceinformation and cause the position of the vibrator assembly to change tomaintain the distance within a distance range automatically.
 30. Thesystem of claim 21, further comprising a laser projector configured forprojecting the images for display on the surface of the screen, whereinthe vibrator assembly is configured to reduce speckle in the imagesdisplayed on the surface of the screen by vibrating at least part of thescreen.